# Homework Help: Energy and temperature

1. Jul 18, 2009

### intenzxboi

1. The problem statement, all variables and given/known data

A 5-g coin is dropped from a 300-m building. If it reaches a terminal velocity of 45 m/s, and the rest of the energy is converted to heating the coin, what is the change in temperature (in °C) of the coin? (The specific heat of copper is 387 J/kg °C.)

I have no idea how to start the problem..

2. Jul 18, 2009

### rock.freak667

3. Jul 18, 2009

### intenzxboi

So...
Potential Energy initial = delta Q?

I don't have a physics book and the teacher pdf notes kinda suck can i get the formula for the thermal change in energy

4. Jul 18, 2009

### cepheid

Staff Emeritus
Nope. Not all of it is converted into heat. Obviously if the object starts at 0 m/s and ends up at 45 m/s, it has gained some kinetic energy too.

5. Jul 18, 2009

### intenzxboi

mgd= delta q + KE?

6. Jul 18, 2009

### songoku

No
Total energy before the coin is dropped = total energy after it reaches terminal velocity
What is/are the energy/energies present before it is dropped?
What is/are the energy/energies present after it reaches terminal velocity?

7. Jul 18, 2009

### songoku

Sorry i'm late....
the last one is right

8. Jul 18, 2009

### cepheid

Staff Emeritus
Yes.

9. Jul 18, 2009

### intenzxboi

(.005)(9.8)(300) = (5)(387)T + (.5)(.005)(45^2)

So t = 4.98
does that look right?

10. Jul 18, 2009

### intenzxboi

my other question is if i did it like that wouldn't the units for my answer be 4.98 kg/J = delta T ??

11. Jul 18, 2009

### songoku

the number is right but not the unit. What is the unit for temperature?

12. Jul 18, 2009

### intenzxboi

o0o got it C the kg and J cancels out

13. Jul 18, 2009

### intenzxboi

thanks for all the help